A random copolymer poly(4-vinylpyridine-co-acrylonitrle) (designated as P4VP-r-AN) was synthesized by solution polymerization, and characterized by the average viscosity molecular weight measurement, along with 1H NMR, 13C NMR, DSC, and FTIR spectroscopy. The viscosity-average molecular weight of the P4VP-r-AN is 1.06×104 g/mol, and the mass content of P4VP is about 87.1%. A new method based on ionic self-assembly technology was provided for design of side chain azocomplex (P4VP-r-AN/MY) from the protonated P4VP-r-AN (P4VP＋-r-AN) and azobenzene dye metanil yellow (MY) in aqueous solution. The self-assembly behaviors and morphologies of P4VP-r-AN/MY were investigated by means of 1H NMR, FTIR, DSC, UV-vis, SEM, TEM and High-resolution transmission electron microscopes and X-ray energy dispersion spectrometer (HRTEM&EDS). It was found that azobenzene complex P4VP-r-AN/MY could be self-assembled and aggregated in aqueous solution, and the aggregations shown to be solid polymeric nanospheres on the sizes of 10～200 nm in diameters. The molar ratio of MY and P4VP-r-AN in P4VP-r-AN/MY was measured at about 0.575. HRTEM&EDS were used to study the morphology and composition of the organic nanospheres. The EDS elemental analysis indicated that the spherical organic nanoparticles are indeed composed of MY dye molecules.